Synthetic resin bottle having a gradation pattern, and process for injection molding the preform for use in such a bottle

ABSTRACT

The technical problem to be solved by the invention is to change the thickness of the colored resin layer of the preform gradually in the upward or downward direction, by utilizing a tendency of gradual decrease in the thickness of the colored resin layer caused by the flow of the main resin inside the preform mold when the main resin and the colored resin are injected into the mold. The objects of this invention is to provide a biaxially drawn, blow molded bottle having new decorativeness created in which sophisticated color gradations associated with color density are created in the body of this bottle. The means of accomplishing this object involves adjusting the injection pattern including the time of starting and ending the supply of the main resin and the colored resin, and pressure or velocity profiles, reducing the thickness of the colored resin layer in the multi-layered molten resin fluid gradually at an upstream or downstream point of the flow, injection-molding the preform in which a color-gradated portion associated with the thickness of the colored resin layer has been formed, and biaxially drawing and blow molding this preform into a bottle having a color-gradated portion associated with the color density or color shade created on the body of the bottle.

This is a Division of application Ser. No. 11/884,311 filed Aug. 14,2007, which in turn is a National Phase of Application No. JP2006-308515 filed Apr. 24, 2006, which claims the benefit ofApplications JP 2005-132961 filed Apr. 28, 2005; JP 2005-160282 filedMay 31, 2005; JP 160477 filed May 31, 2005; and JP 2005-160478 filed May31, 2005. The disclosure of the prior applications is herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

This invention relates to a synthetic resin bottle decorated with agradation pattern, and to a process for injection molding the preform tobe biaxially drawn and blow molded into this bottle.

BACKGROUND ART

Bottles made of the polyethylene terephthalate (PET) resin are utilizedin various fields, including drinks, foods, and cosmetics. Methods ofdecorating the bottles are also wide-ranging with an intention todifferentiate the merchandise. In many cases, bottles are decorated withprinted shrink film. Patent document 1 describes a bottle obtained byblow-molding a preform having a laminar structure in which a coloredintermediate layer has been formed intermittently.

-   [Patent document 1] JP2-98409 A

DISCLOSURE OF THE INVENTION Technical Problems to be Solved by theInvention

Inventors of this invention worked on the development of a technologyfor bottle decorations by changing color density in the upward ordownward directions in a biaxially drawn, blow-molded transparent bottlemade of a PET resin to create color gradations caused by a change incolor density. It was found from their tests that the process describedin the patent document 1 was unsatisfactory from a point of view ofdecorativeness because gradations in color were limitative, thoughpossible, when a preform was provided with the intermediate layer of acolored resin and was biaxially drawn and blow molded into the bottle.

More specifically, the colored resin layer in the above-describedconventional technology has a structure in which its thickness isincreased or decreased in a continued manner. The color gradationcreated as a color pattern is the gradation inside the color-decoratedarea formed by this colored resin layer. Therefore, it is difficult toput an emphasis on the gradation. Especially in light colors, a problemarises from the difficulty in creating a gradation pattern.

As another problem, the flow of a molding resin material is widelychanged when the material is injected into the mold by the injectingmachine. Therefore, any increase or decrease in the thickness of thelayer of an injected colored resin that has been formed inside theinjecting machine is not always reflected on the change in the thicknessof the layer of the colored resin formed inside the mold. For thisreason, it is difficult to obtain a decoration based on the colorgradation. Even if such a decoration is obtained, the form of colordecoration is not constant, and it is quite difficult to commercialize abottle having such a decoration.

Still another problem is that the control of the injecting machineoperation is troublesome and difficult. The injecting behavior of a mainresin is affected by the changes in the injection rate for the coloredresin. Thus, it is necessary to precisely align the injecting behaviorof the main resin with that of the colored resin. Such alignment isdifficult.

The technical problem to be solved by the invention is to utilize atendency of gradual decrease in the thickness of the layer of thecolored resin caused by the flow of the main resin inside the preformmold when the main resin and the colored resin are injected into themold and to change the thickness of the intermediate layer or thecolored resin layer of the preform gradually in the upward or downwarddirection. The objects of this invention is to provide a biaxiallydrawn, blow molded bottle having new decorativeness created bysophisticated color gradations caused by the changes in color density.

It is also a technical problem of this invention to form a preformhaving multiple colored layers of a laminar structure, in which eachlayer is made of a colored resin of a different color shade and tochange the thickness of these colored layers gradually in the upward ordownward direction. Thus, another object of this invention is to providea biaxially drawn, blow molded synthetic resin bottle havingunconventional decorativeness created by sophisticated color gradationscaused by the change in color density, color shade, or both.

Means of Solving the Problems

The invention according to claims 1 to 12, among other claims of thisinvention, relate to the bottle decorated with gradation patterns. Themeans of carrying out the invention of claim 1 is a synthetic resinbottle obtained by biaxially drawing and blow molding a preform havingthe shape of a bottomed cylinder. The bottle has a gradation pattern incolor, wherein a portion of cylindrical body of the bottle has a laminarstructure in which a main resin layer made of a main resin is laminatedwith a colored resin layer made of a colored resin of another color,wherein a color-decorated portion is created by this colored resinlayer, and wherein a color-gradated portion is created by a thinboundary area which is an end portion of the colored resin layer andwhere the colored resin layer has gradually reduced its thickness.

In the invention of claim 1, the color-gradated portion showing agradation pattern is created by a thin boundary area of the upper and/orlower end of the colored resin layer. The gradation of color caused bythe change in the thickness of the colored resin layer in the thinboundary area is emphasized in the background of the color of the mainresin layer.

The color-gradated portion of the bottle is formed in the thin boundaryarea of the colored resin layer when the preform is biaxially drawn andblow molded into the bottle. At that time, the thin boundary area of thepreform is further thinned by the biaxial drawing and blow molding, andthere appears the color-gradated portion.

The invention of claim 2 includes the configuration of the invention ofclaim 1 and also comprises that a transparent resin material is used foreach of the main resin for molding the main resin layer and the coloredresin for molding the colored resin layer.

In the invention of claim 2, any slight change in color in thecolor-gradated portion can be visualized, and thus, it is possible towiden the range of the color-gradated portion reasonably.

The means of carrying out the invention of claim 3 is a preform, which,in the invention of claim 1 or 2, is injection-molded into a bottomedcylindrical shape having a gate imprint at the center of bottom andwhich comprises the main resin layer, made of a main resin that formsthe preform almost entirely, and the colored resin layer made of acolored resin having a different color from the color of the main resinand having been laminated with the main resin layer to become at least apart of the body of the preform, wherein an end portion of the coloredresin layer in the body wall of the preform is gradually reduced inthickness by the flow behavior of the main resin during the injectionmolding to form the thin boundary area.

In the invention of claim 3, the colored resin is injected into the moldfrom the injecting machine to mold the preform. The material flowstogether with the main resin, and forms in the mold a cylindrical shape.Thus, the colored resin layer is formed in the position where this layeris laminated with the main resin layer made of the main resin.

The cavity of the mold for molding the preform body serves also as thepassage for the molding materials injected into the mold. Both the mainresin and the colored resin flow actively, while affecting each other.The flow behavior of the main resin has a strong impact especially onthe end portion of the colored resin layer (the downstream and/orupstream portion along the flow direction of molten resins). Therefore,the end portion of the colored resin layer is gradually reduced inthickness toward the end of the layer to form the thin boundary area.

Under this configuration of the preform, the end portion of the coloredresin layer disposed in the body wall is gradually reduced in thickness.When such a preform is biaxially drawn and blow molded into a bottle,the thin boundary area is more and more thinned to create acolor-gradated portion where the gradation of color is continuous andlight.

The timing of injecting the colored resin almost accurately determinesthe position of the thin boundary area on the body of the preform. As aresult, it becomes possible to obtain a bottle decorated with a colorgradation pattern stably.

The invention of claim 4 includes the configuration of the invention ofclaim 1, 2, or 3, and also comprises that the colored resin layer isembedded in the main resin layer.

The invention of claim 4 is concerned with an actual laminar structurefor the main resin layer and the colored resin layer. In the inventionof claim 4, various color patterns are created by the colored resinlayer when this layer is affected by the color and/or transparency ofthe main resin layer.

The means of carrying out the invention of claim 5 comprises that thebiaxially drawn, blow-molded synthetic resin bottle in the invention ofclaim 4 has an intermediate layer made of a colored resin and formed ina certain height range, wherein the bottle is decorated with colorgradations caused by a change in color density when the thickness ofthis intermediate layer is gradually reduced in the upward or downwarddirection at the upper or lower end of this layer.

In the invention of claim 5, there can be provided the bottle having newdecorativeness in which sophisticated color gradation caused by thechange in color density has been created by the intermediate layer.

The means of carrying out the invention of claim 6 comprises that thebottle according to claim 5 of this invention is made of a PET resin andthat color gradation has been achieved in such a way that the bottlewall changes gradually and continuously from a colored transparent stateto a colorless transparent state over the area from the upper end of theshoulder down to the bottom.

In the invention of claim 6, there can be provided a PET bottle havingnew decorativeness, in which color gradation has been achieved in such away that the bottle wall changes gradually and continuously from acolored transparent state to a colorless transparent state over the areafrom the upper end of the shoulder down to the bottom. The portionranging from the top of the neck to the shoulder can also be decoratedin color.

The means of carrying out the invention of claim 7 comprises that, inthe invention of claim 4, 5, or 6, a preform is used, which is molded byinjecting molten resins into the mold through the gate disposed at aposition opposed to the center of the bottom and is characterized byhaving an intermediate layer made of a colored resin and formed in acertain height range and by having a color-gradated portion created by achange in the thickness of the intermediate layer at its upper- or lowerend when the thickness is gradually reduced in the upward or downwarddirection.

In the invention of claim 7, the preform has the intermediate layer inwhich a color-gradated portion is created by the change in the thicknessof this intermediate layer at its upper- or lower end when the thicknessis gradually reduced in the upward or downward direction. This preformis biaxially drawn and blow molded into a bottle having newdecorativeness, in which sophisticated color gradation caused by thechange in color density has been created by the intermediate layer madeof the colored resin.

The means of carrying out the invention of claim 8 comprises that, inthe invention of claim 7, the change in the intermediate layer thicknessfor the color-gradated portion is shown by a condition of L/t1≧30 whereL is the length of the color-gradated portion and t1 is the layerthickness at the base of the color-gradated portion.

The above-described configuration of claim 8 is intended to specify theextent of color gradation created by the change in thickness of theintermediate layer formed in the preform to be used. Under the conditionof L/t1≧30, the layer thickness for the color-gradated portion isreduced as slowly as never before. As a result, there can be provided abottle having new decorativeness, in which the color gradation effectderived from color density, coupled with the drawing effect from biaxialdrawing and blow molding, has been created synergistically in asophisticated manner.

The invention of claim 9 comprises that, in the invention of claim 1, 2,or 3, the colored resin layers are disposed on both of outer and innersurfaces of the main resin layer.

The invention of claim 9 relates to an actual laminar structure for themain resin layer and the colored resin layer, that is different from thelaminar structure of claim 4. In the invention of claim 9, the colorpattern created on the bottle walls is not affected by the color and/ortransparency of the main resin layer, but truly corresponds to thecolored resin layer of the preform.

The means of carrying out the invention of claim 10 comprises that, inthe invention of claim 9, colored layers are formed on the body of thebottle by a colored resin in the shape of double cylinders disposed inthe inner- and outer-surface vicinities in a certain height range andthat the thickness of these colored layers are reduced gradually in theupward direction to decorate the bottle with color density gradations.

In the invention of claim 10, it is possible to provide the bottlehaving new decorativeness in which highly sophisticated color densityradiations.

The means of carrying out the invention of claim 11 comprises that thebottle in the invention of claim 10 is made of a PET resin and thatcolor density gradations are appeared changing gradually andcontinuously in the upward direction from the colored transparent stateto the colorless transparent state in a certain height range coveringfrom near bottom to shoulder.

In the invention of claim 11, there can be provided a PET bottle havingnew decorativeness, in which color gradations have been achieved in sucha way that the bottle wall changes gradually and continuously from acolored transparent state to a colorless transparent state over the areafrom the shoulder down to the vicinity of the bottom.

The means of carrying out the invention of claim 12 comprises that, inthe invention of claim 9, 10, or 11, a preform is molded by a successiveinjection molding process, in which the colored resin is primarilyinjected as a short shot into the mold cavity by way of a gate disposedat the position opposed to the center of the bottom, followed by thesecond injection of main resin, i.e., the main raw material for moldingthe preform, with this second injection being given after a lapse ofpredetermined waiting time. The preform has colored resin layers in theshape of double cylinders in the inner and outer surface vicinities, andthe thickness of these colored layers is gradually reduced in the upwarddirection to form color-gradated portions.

In the invention of claim 12, the preform has colored resin layers inthe shape of double cylinders in the inner and outer surface vicinitiesand has layer thickness reduced gradually in the upward direction toform color-gradated portions. This preform is biaxially drawn and blowmolded into the bottle having new decorativeness in which highlysophisticated color gradations caused by the change in color density arecreated by these colored layers.

The invention according to claims 13 to 21 relates to a preform-moldingprocess, and especially to a molding process for the preform to bebiaxially drawn and blow molded into the bottle decorated with agradation pattern, according to the invention of claims 4 to 8, in whichthe above-described colored resin layer is embedded in the main resinlayer. The molding process in the invention of claim 13 generallycomprises;

flowing molten synthetic resins through at least three layer-formingchannels of a cylindrical inner flow channel, a middle flow channel, anda cylindrical outer flow channel;

flowing the resins through a confluence disposed downstream of theselayer-forming channels and through a joined flow channel;

passing the resins through a gate disposed at a position opposed tocenter of bottom; and

injecting the resins into mold to form a preform; and further comprises:

supplying the inner flow channel and the outer flow channel with themain resin for the preform from at least one loader at a predeterminedtime span, pressure, or velocity;

supplying the middle flow channel with a colored resin from anotherloader at a predetermined pressure and/or velocity during apredetermined time within said time span;

allowing the colored resin to join the main resin from the inner flowchannel and the outer flow channel at the confluence in such a mannerthat the layer of colored resin is sandwiched between the two layers ofthe main resin;

forming a multi-layered molten resin fluid having an intermediate layerof the colored resin between the layers of main resin within the joinedflow channel over a certain span of time;

adjusting the injection pattern including the time of starting andending the supply of the colored resin, pressure, or velocity profiles;and

reducing the thickness of this intermediate layer at an upstream ordownstream point of the flow gradually in the upstream or downstreamdirection so as to form a color-gradated portion.

In what is called the simultaneous injection molding, a gas barrierresin that forms the intermediate layer is injected together with themain resin, i.e., the main raw material for preform, for a certainperiod within a span of time when the main resin is being injected. Insuch a process, the inventors of this invention have found that an endof the intermediate layer is not cut instantly but is gradually drawnand reduced in thickness, depending on the condition of injection, andhave made this invention from that discovery. It should be noted herethat claim 13, along with later described claims 15 and 17, describes“pressure and/or velocity” to include the cases where both the pressureand the velocity are set in controlling the supplies of resins becausethe injection molding process of this invention is carried out bysetting the resin supply pressure or velocity or both at predeterminedlevels.

According to the molding process of claim 13, the colored resin flowsthrough the middle flow channel, and at the confluence, is sandwichedbetween the main resin fluids coming from the inner and outer flowchannels to form the intermediate layer. At the time when the coloredresin starts flowing in or comes to the end of flow, an end of thisintermediate layer deforms under the interaction between the end of thecolored resin fluid and the main resin fluids coming from the inner andouter flow channels.

At that time, the injection pattern is adjusted, including the time ofstarting and ending the supply of colored resin, and the supply pressureand/or velocity profiles. This adjustment allows an end of theintermediate layer to be deformed by the shearing flow or theelongational flow to assume the shape of a wedge or a graduallynarrowing thread, as viewed in the vertical section.

By reducing the layer thickness gradually in the upstream or downstreamdirection, it is possible to form a color-gradated portion caused by thechange in thickness. If the preform thus molded is biaxially drawn,color gradations are created by the change in color density in theupward or downward direction, and there is provided a synthetic resinbottle newly decorated with such gradations. The middle flow channel tobe used by the colored resin is not limited to a cylindrical shape, butcan be in the cross-sectional shape of, for example, a thin-platerectangle. The flow channel in such a shape leads to a bottle decoratedwith the colored resin layer having vertical strips of gradations thatextend in the upward or downward direction in the predetermined area ofthe molded product.

The molding process according to the invention of claim 14 comprisesthat, in the invention of claim 13, the middle flow channel is alsodisposed coaxially as a cylindrical channel together with the inner andouter flow channels.

The molding process of claim 14 enables the color-gradated portionassociated with the thickness of the intermediate layer to be formed inthe upward or downward direction around the entire preform body. Thus, abottle can be provided, in which color gradations caused by the changein color density are created sophisticatedly in the upward or downwarddirection around the body of the bottle.

The molding process according to the invention of claim 15 comprisesthat, in the invention of claim 13 or 14, the supply pressure and/orvelocity is gradually reduced at the time when the supply of the coloredresin comes to an end, so that a color-gradated portion is formed at theupstream end of the intermediate layer.

Based on the molding process of claim 15, the supply pressure and/orvelocity is gradually reduced at the ending point of time. As a result,the volume of supply resin or the thickness of the intermediate layer isreduced toward the upstream. The upstream end is extended and deformedto assume the shape of a gradually narrowing thread, as viewed in thevertical section.

The molding process according to claim 16 comprises that, in theinvention of claim 13, 14, or 15, the colored resin is allowed to remainin the vicinity of the confluence where the colored resin joins the mainresin, at the time when the supply of the colored resin comes to an endand that this remaining colored resin is drawn by the flow of the mainresin in the downstream direction to form a color-gradated portion inthe shape of a gradually narrowing thread at the upstream end of theintermediate layer.

After the supply of the colored resin is stopped, the force of advancingthe colored resin flow from upstream of the middle flow channel does notact on the colored resin remaining at the confluence of the middle flowchannel. In the molding process of claim 16, the force of the main resinflow acts on the remaining colored resin to draw and deform so that thethickness of the intermediate layer is changed at the upstream end toassume the shape of a gradually narrowing thread.

The molding process according to the invention of claim 17 comprisesthat, in the invention of claim 13. 14. 15. or 16, the supply pressureand/or velocity is gradually increased at the time when the supply ofcolored resin is started, so that a color-gradated portion is formed atthe downstream end of the intermediate layer.

In the invention of claim 17, the pressure and/or velocity of coloredresin supply is gradually increased when the supply is started. In otherwords, the volume of the supplied resin, or the thickness of theintermediate layer, is increased in the upstream direction. In thismanner, a color-gradated portion thus formed shows a gradually narrowingthread in the downstream direction.

The molding process according to the invention of claim 18 comprisesthat, in the invention of claim 13, 14, 15, 16, or 17, the colored resinhas a molten viscosity that is lower than the viscosity of the mainresin so that the intermediate layer of the multi-layered molten resinfluid is deformed to assume the shape of a gradually narrowing thread ateither upstream or downstream end.

In the molding process of claim 18, either end of the intermediate layeris deformed at or near the confluence when it is affected by the actionof the main resin flows coming from the inner and outer flow channels.If the colored resin has a low viscosity, this action proceedseffectively, and the layer thickness at one end can be changed to theshape of a gradually narrowing thread. Especially in the case ofextending deformation, the low viscosity prevents the molten resin frombeing discontinued and easily achieves the change into the graduallynarrowing thread.

The molding process according to the invention of claim 19 comprisesthat, in the invention of claim 13, 14, 15, 16, 17, or 18, a valve toopen or close the channel is disposed between the colored-resin loaderand the middle flow channel and that the color-gradated portion isformed at either downstream or upstream end of the intermediate layer ofthe multi-layered molten resin fluid, depending on the type of thisvalve or the switching method.

Since resins have viscoelastic properties, the type of valve or theswitching velocity can be adjusted in the molding process of claim 19 sothat the colored resin pressure is changed delicately at the confluencewhen the supply of colored resin begins or comes to an end. As a result,it is possible for the upstream or downstream end of the intermediatelayer to have the layer thickness effectively changed into the shape ofa gradually narrowing thread. If use is made of, for example, a valvecapable of quickly opening or closing the flow, such as a ball valve,then the supply of colored resin can be brought to a stop at once, andthe upstream end of the intermediate layer is drawn to reduce the layerthickness effectively into the shape of a gradually narrowing thread.

The molding process according to the invention of claim 20 comprisesthat, in the invention of claim 13, 14, 15, 16, 17, or 19, use is madeof two loaders and three layer-forming channels of an inner flowchannel, a middle flow channel, and an outer flow channel and that themain resin from one loader is supplied to both the inner flow channeland the outer flow channel, and that the colored resin, i.e., coloredmain resin, from the other loader is supplied to the middle flowchannel.

The molding process of claim 20 relates to a practical laminarstructure. The entire preform is made of the same resin, regardless ofcolored resin or not, and stable molding operation can be accomplishedby using the same resin.

The molding process according to the invention of claim 21 comprisesthat, in the invention of claim 13, 14, 15, 16, 17, 18, 19, or 20, boththe main resin and the colored resin are transparent materials.

The molding process of claim 21 can create the color gradation effectmore visibly by the transmission of light. Thus, the bottle having a newdecorative effect can be provided.

This invention according to claims 22 to 27 also relates to thepreform-molding process, and in particular, to the preform-moldingprocess wherein the preform thus obtained is biaxially drawn and blowmolded into the bottle decorated with gradation patterns in whichcolored resin layers are disposed on both of outer and inner surfaces ofthe main resin layer, as described in the invention according to claims9 to 12. The molding process in the invention of claim 22 is a processfor molding a preform for use in biaxial drawing and blow molding, whichcomprises:

giving a primary injection of colored resin as a short shot to the moldcavity by way of the gate located at a position opposed to the center ofbottom;

after a lapse of waiting time from the end point of primary injection,giving successively a secondary injection of main resin, i.e., the majormaterial forming the preform;

adjusting this waiting time so that the main resin from the secondaryinjection is allowed to flow through the cavity in a manner in which themain resin penetrates the central part of the colored resin locatedinside the cavity of the mold in the short shot state;

forming colored layers made of the colored resin in the shape of doublecylinders at positions near the inner surface and outer surface of thepreform; and

thus forming color-gradated portions where the colored layers arereduced in thickness in the upward direction of the preform.

According to the molding process of claim 22, the colored resin isinjected as a short shot in the primary injection, which is followed bythe secondary injection of main resin after a predetermined lapse ofwaiting time. In this way, the lapse of waiting time allows the shortshot of colored resin to cool in and near the portion coming in contactwith cavity mold surface and core mold surface (hereinafter collectivelyreferred to as mold surface vicinity). The resin in this portion coolsand solidifies, or molten viscosity increases progressively. Byadjusting and setting a suitable waiting time, it is possible to proceedwith the cooling of the primarily injected colored resin in the moldsurface vicinity, while retaining a high temperature in the central partof the cavity.

If the main resin is secondarily injected in a successive manner underthe above-described condition, the main resin in the molten state passesthrough the gate at the position opposed to the bottom center of thepreform, and then through the central part of the colored resin in thecavity. The main resin flows toward the portion corresponding to the topend of the neck to fill the cavity, while dragging a part of the coloredresin. At that time, the colored resin located in the mold surfacevicinity, especially the resin quite near the mold surfaces, does notflow, but remains at the primarily injected position. On the other hand,some molten colored resin is dragged in the flowing direction. As aresult, the colored resin, especially the forefront of the flow, has agradually reduced thickness in the flow direction to form acolor-gradated pattern.

In the preform molded by successive injections such as described above,the colored resin layers made of a colored resin are formed in doublecylinders on the inner and outer surfaces of the main resin layer. Thesecolored resin layers have a gradually reduced thickness in the upwarddirection of the preform to form a color-gradated portion. Depending onthe molding condition or the height position of the preform, the mainresin layers of thin film are formed on the inside and/or outside ofthese colored layers, thus forming the innermost surface and/oroutermost surface. For this reason, the term “inner and outer surfacevicinity” is used to include these innermost and/or outermost surfaces.

As described above, a technical idea for the molding process of claim 22involves setting a suitable waiting time between the primary injectionand the secondary injection in a successive injection molding processand utilizing the difference in the extent of cooling between the moldsurface vicinity and the central part of the colored resin injected intothe cavity as a short shot, whereby a part of the colored resin isdragged in the flowing direction by the flow of the later-injected mainresin to form color-gradated portions caused by the change in layerthickness

The extent of thickness-related color gradation or the change in layerthickness can be controlled by the conditions of successive injections,such as the volumes of primary and secondary injections, the injectionvelocity, pressure, and temperature, and the waiting time, and also bythe molten viscosity of the resin in use.

The molding process in the invention of claim 23 comprises that, in theinvention of claim 22, the extent of color gradation caused by thechange in thickness of the colored layers is controlled by a combinationof the waiting time, the secondary injection velocity, and the injectionpressure.

In this method of claim 23, the extent of color gradation caused by thechange in thickness of the colored layers can be controlled relativelyeasily by adjusting the waiting time, the secondary injection velocity,and the injection pressure. If a short waiting time, a fast secondaryinjection velocity, and a high injection pressure are used, the layerthickness can be changed slowly to form gradually narrowing threads atthe forefront of colored layers.

The molding process in the invention of claim 24 comprises that, in theinvention of claim 22 or 23, the colored main resin is used as thecolored synthetic resin.

The molding process of claim 24 ensures that the entire preform ismolded by the same resin. The preform can be molded stably because thecolored resin and the main resin are made of the same resin.

The molding process in the invention of claim 25 comprises that, in theinvention of claim 22, 23, or 24, the colored resin has a relatively lowmolten viscosity than that of the main resin.

In the molding process of claim 25, the short shot of colored resindeforms as it is affected by the main resin flow that passes through thecentral part. If the colored resin has a low viscosity, this action ofthe flow becomes more effective, and the layer thickness can be changedto the shape of a gradually narrowing thread at the forefront.

The molding process in the invention of claim 26 comprises that, in theinvention of claim 22, 23, 24, or 25, both the main resin and thecolored resin are transparent resins.

The molding process of claim 26 can create the color gradation effectcaused by the change in color shades much more visibly through thetransmission of light. Thus, the bottle having a new decorative effectcan be provided.

The molding process of claim 27 comprises that, in the invention ofclaim 22, 23, 24, 25, or 26, a preliminary injection of the main resinis given in a predetermined amount before the primary injection.

In the case of successive injection molding process of this invention, aseries of basic operations include the primary injection of coloredresin, the waiting time, and the secondary injection of main resin. Themolding process of claim 27 involves injecting a predetermined amount ofthe main resin before the primary injection. Depending on the purpose ofdecoration for the bottle, the position at which colored layers areformed on the preform can be arbitrarily set by injecting apredetermined amount of main resin before the primary injection.

At the time of primary injection of colored resin after the preliminaryinjection, the colored resin is forced to pass through the central partof a short shot of the main resin that has been injected preliminarily,while dragging this main resin over the mold surfaces. In this manner,both the outer surface (outermost layer) and the inner surface(innermost layer) can be constructed with this main resin. Since thecontents of the bottle do not come in direct contact with the coloredresin, the user feels at ease in utilizing the bottle.

The invention of claims 28 to 32 also relates to the preform-moldingprocess, and in particular, to a process for molding a preform havingmultiple colored resin layers of a laminar structure, in which eachlayer is made of a colored resin of a different color shade, and inwhich the thickness of these colored resin layers is gradually changedin the upward or downward direction. Among others, the molding processin the invention of claim 28 is a process for molding a preform for usein biaxial drawing and blow molding, in which multiple resins includingat least one colored resin are successively injected into the cavity ofa mold by way of a gate located at the position opposed to the center ofbottom, and which comprises injecting initially a short shot of acolored resin into the cavity of the mold, then injecting a second resinand letting the second resin wedge its way through central part of theearlier injected colored resin to form laminated layers, and forming acolor-gradated portion in the colored layer in such a way that thicknessof the colored layer made of the first colored resin injected earlier isgradually reduced toward the bottom.

According to the molding process of claim 28, the earlier injectedcolored resin existing in the mold cavity in the state of a short shothas a higher resin temperature and a lower molten viscosity at thecentral part distant from the cavity wall than in the vicinity of thecavity wall. The later injected resin wedges its way through thiscentral part. As a result, the colored layer made of the earlierinjected resin comes to have a portion with its thickness reducedgradually in the upstream direction toward the gate position.

In the preform thus molded, it is possible for the colored layer made ofthe earlier injected colored resin to have a color-gradated portionassociated with the thickness of the colored layer that is reduced inthe direction toward the bottom.

In the molding process of claim 28, preforms in various laminarstructures can be obtained for any purpose of decoration by thesuccessive molding in the steps illustratively shown below. Thesepreforms can be biaxially drawn and blow molded into bottles variouslydecorated in colors.

(1) A colored transparent resin/A colorless transparent resin(2) A colored transparent resin/A colorless transparent resin/A coloredtransparent resin(3) A colored transparent resin/A transparent resin of a differentcolor/A colorless transparent resin(4) A colored transparent resin/A transparent resin of a differentcolor/A transparent resin of still another color/A colorless transparentresinOf course, depending on the purpose, there can be utilized not onlytransparent resins but also translucent or opaque resins. The sameresins with different colors or the resins of different types, too, canbe utilized.

For example, in the case of (3), resins are successively injected in theorder of the first colored transparent resin, the second transparentresin in a color different from the first resin, and the third colorlesstransparent resin. The second resin wedges its way through the centralpart of the first resin inside the cavity. Then, the third resin wedgesits way through the central part of the second resin. Consequently, thepreform has color-gradated portions associated with the thickness of thecolored layers in such a way that the color-gradated portion created bythe first colored transparent resin overlaps partially that of thesecond colored transparent resin. When such a preform is biaxially drawnand blow molded into a bottle, there can be provided the bottledecorated with gradations in which color density and color shade changetogether gradually and continuously.

The extent of gradations caused by the thickness of colored resinlayers, i.e., the aspect of change in thickness, can be controlled forany purpose by such conditions as the volume of injection, the speed andpressure of injection, the temperatures of injected resins, and the moldtemperature for each resin, and by the levels of molten viscosity ofresins to be used.

The molding process of the invention according to claim 29 comprisesthat the extent of gradation associated with the thickness of thecolored layer made of the earlier injected colored resin is controlledby a combination of injection speed and pressure of the later injectedresin.

The above-described process of claim 29 ensures that the extent ofgradation associated with the thickness of the colored layer can berelatively easily controlled by the combination of the speed andpressure of injection among other conditions of successive injections.

The molding process of the invention according to claim 30 comprisesthat, in the invention of claim 28 or 29, the resins are successivelyinjected in 3 steps.

Resins are successively injected in 3 steps according to the moldingprocess of claim 30. This process can be accomplished relatively easilyfrom the aspects of equipment and process steps. As shown below, resinscan be injected in 3 steps in various combinations of 2 or 3 resins thatgive the bottle different color shades, depending on the purpose ofdecorations.

(1) A colorless transparent resin/A colored transparent resin/Acolorless transparent resin(2) A colored transparent resin/A colorless transparent resin/Atransparent resin of the same color(3) A colored transparent resin/A colorless transparent resin/Atransparent resin of a different color(4) A colored transparent resin/A transparent resin of a differentcolor/A colorless transparent resin(5) A colored transparent resin/A transparent resin of a differentcolor/A transparent resin of still another colorAs the base resin except for the coloring components, the same resin canbe utilized in all the combinations. One of the resins may have a lowmolten viscosity, or resins of different types can also be used.Depending on the purpose, translucent or opaque resins or colored opaqueresins can also be used.

The molding process of the invention according to claim 31 comprisesthat in the invention of claim 28, 29, or 30, the colored resin to beinjected earlier has a lower molten viscosity than the later injectedresin has.

The molding process of claim 31 ensures that the later injected resinwedges its way through the central part of the earlier injected coloredresin in the state of a short shot to form a color-gradated portion inthe preform. Since the colored resin is given a low molten viscosity inthe molding process of claim 31, this color-gradated portion is formedmore effectively than before, and the thickness of the colored resin canbe reduced to have the shape of a gradually narrowing thread, as viewedin the vertical section of the body wall.

The molding process of the invention according to claim 32 comprisesthat, in the invention of claim 28, 29, 30, or 31, each resin used inthis process is a transparent resin.

The molding process of claim 32 makes it possible to create acolor-gradated effect caused by color density or color shade due to thelight transmission through the bottle, which is the end product, and toprovide the bottle having a new decorative effect.

The means of carrying out the invention of claim 33 is a preform for usein biaxial drawing and blow molding, which is molded by the successiveinjection process, in which multiple resins including at least onecolored resin are successively injected into the cavity of the mold byway of the gate located at the position opposed to the center of thebottom. This preform is characterized in that having a color-gradatedportion formed by the colored resin layer made of the earlier injectedcolored resin, with thickness of the colored resin layer in this portionbeing gradually reduced toward the bottom by the flow action of thesecond resin that wedges its way through the central part of the earlierinjected colored resin.

The preform of claim 33 having above-described configuration can beobtained by the successive injection molding process described in claims28 to 32. This preform is biaxially drawn and blow molded into a bottlehaving new decorativeness, in which sophisticated color gradationderived from the change in color density, color shade, or both iscreated by the colored resin layer made of a colored resin.

The invention according to claims 34 and 35 relates to a bottle. Themeans of carrying out the invention of claim 34 is a synthetic resinbottle obtained by biaxially drawing and blow molding the preform whichis molded by the successive injection process in which multiple resinsincluding at least one colored resin are successively injected into thecavity of the mold by way of the gate located at a position opposed tothe center of the bottom. This preform has a color-gradated portionformed by the colored layer made of the earlier injected colored resin,and the thickness of the colored layer in this portion is graduallyreduced toward the bottom by the flow action of the second resin thatwedges its way through the central part of the earlier injected coloredresin. As a result, the bottle is decorated with color gradationscreated by the gradual change toward the bottom in the thickness of thecolored resin layer made of the earlier injected colored resin and bythe subsequent change in color density, color shade, or both, which iscaused to occur in a continuous manner.

The above-described bottle of claim 34 can be obtained from the preformof claim 33 which is obtained by the molding process of claims 28 to 32.This preform is biaxially drawn and blow molded into a bottle having newdecorativeness, in which sophisticated color gradation derived from thechange in color density, color shade, or both is created by the coloredresin layer made of a colored resin.

The means of carrying out the invention of claim 35 comprises that, inthe invention of claim 34, the bottle is made of a polyethyleneterephthalate resin, wherein gradations are created by the continuousand gradual changes in color density and color shade that occur in threecolored resin layers made of three differently colored resins.

From the above-described configuration of claim 35, there can beprovided a PET resin bottle having new decorativeness, in whichsophisticated gradations in three colors are created by the continuousand gradual changes in color density and color shade.

Effects of the Invention

This invention having above-described configurations has the effectsdescribed below. The invention according to claims 1 to 12 relates to abottle decorated with a gradation pattern. Highly decorative effectsderived from the patterns of color gradation can be achieved in theinvention of claim 1 because such patterns of color gradation arecreated by the changes in color density on the bodies of biaxiallydrawn, blow-molded bottles.

The area of the created pattern of gradation can be widened, and gentlecolor density can be achieved to create the pattern of gradation thatgives light decorative effects.

If a transparent resin is used as in the invention of claim 2, the areacovered with a gradation pattern can be widened so reasonably that it iseasy to obtain a large pattern of gradation.

In the invention of claim 3, the preform to be used has a structure inwhich one end of the colored resin layer located on the body has itsthickness reduced gradually to form a thin boundary area. When thispreform is biaxially drawn and blow molded into a bottle, the thinboundary area of the bottle becomes more and more thin, and gives anarea decorated with color gradations in which change in color density iscontinuous and light.

The timing of colored resin injection precisely determines the positionof the thin boundary area at the end of the colored resin layer on thepreform body. The bottle having a stable color gradation pattern can beobtained by this timing of injection.

The invention of claim 4 relates to a practical laminar structure forthe main resin layer and the colored resin layer. In claim 4, thecolored resin layer is embedded in the main resin layer. Under thisconfiguration, various color patterns are obtained due to the colorand/or transparency of the main resin layer.

In the invention of claim 5, the bottle has an intermediate layer madeof a colored resin over a certain height range and is decorated withcolor gradations created by the change in color density when thethickness of this intermediate layer is gradually reduced in the upwardor downward direction.

In the invention of claim 6, there can be provided a PET resin bottlehaving new decorativeness, in which color gradation has been achieved insuch a way that the bottle wall changes gradually and continuously froma dark colored transparent state to a colorless transparent state overthe area from the upper end of the shoulder down to the bottom.

In the invention of claim 7, a color-gradated portion is created by achange in the thickness of the intermediate layer made of a coloredresin wherein the thickness gradually reduced in the upward or downwarddirection. The preform having such a color-gradated portion is biaxiallydrawn and blow molded into the bottle having new decorativeness in whichcolor gradation caused by the change in color density is created.

The invention of claim 8 is intended to specify the extent of colorgradation associated with the colored resin layer thickness of apreform. Under the condition of L/t1≧30, the layer thickness for thecolor-gradated portion is reduced as slowly as never before. When thepreform thus obtained is biaxially drawn and blow molded, there can beprovided a bottle having new decorativeness, in which the colorgradation effect, coupled with the drawing effect fulfilled during thebiaxial drawing and blow molding, has been created synergistically in asophisticated manner.

The invention of claim 9 relates to another practical laminar structurefor the main resin layer and the colored resin layer, and ensures thatthe color pattern created on the bottle walls is not affected by thecolor and/or transparency of the main resin layer, but is faithfullycorrespondent with the colored resin layer of the preform.

In the invention of claim 10, there can be provided a bottle having newdecorativeness in which colored resin layers have been formed on thebody by a colored resin in the shape of double cylinders disposed in theinner- and outer-surface vicinities in a certain height range and inwhich the thickness of these colored resin layers are reduced graduallyin the upward direction to decorate the bottle with sophisticated colorgradations associated with the change in color density of the coloredresin layers.

In the invention of claim 11, there can be provided a PET bottle havingnew decorativeness, in which color gradations have been achieved in sucha way that the bottle wall changes gradually and continuously from acolored state to a colorless state over the area from the vicinity ofthe bottom up to the shoulder.

In the invention of claim 12, a bottle having sophisticated colorgradations associated with the change in color density can be providedby the colored resin layers made of a colored resin in the shape ofdouble cylinders and disposed in the inner- and outer-surfacevicinities. Such a bottle can be molded by biaxially drawing and blowmolding the preform having color-gradated portions caused by the gradualreduction of layer thickness in the upward direction.

The invention according to claims 13 to 21 relates to a preform-moldingprocess, and in particular, to a preform-molding process wherein thepreform is biaxially drawn and blow molded into the bottle having agradation pattern in which a colored resin layer is located inside themain resin layer. In the invention of claim 13, the injection pattern isadjusted, including the time of starting and ending the supply ofcolored resin, and the supply pressure and/or velocity profiles. Becauseof this adjustment, an end of the intermediate layer is deformed by theshearing flow or the elongational flow to assume the shape of a wedge ora gradually narrowing thread, as observed in the vertical section. Byreducing the layer thickness gradually in the upstream or downstreamdirection, it is possible to form a color-gradated portion caused by thechange in thickness.

In the invention of claim 14, the color-gradated portion associated withthe thickness of the intermediate layer can be formed in the upward ordownward direction around the entire preform body. When this preform isbiaxially drawn and blow molded, a bottle can be provided, in whichsophisticated color gradations caused by the change in color density arecreated in the upward or downward direction around the body of thebottle.

In the invention of claim 15, the supply pressure and/or velocity isgradually reduced at the end of the colored resin supply. As a result,the volume of supplied resin or the thickness of the intermediate layeris reduced toward the upstream. The upstream end is extended anddeformed to assume the shape of a gradually narrowing thread, as viewedin the vertical section.

In the invention of claim 16, the force of advancing the colored resinflow from upstream of the middle flow channel does not act on thecolored resin remaining at the confluence of the middle flow channelafter the supply of the colored resin has been stopped. When the forceof the main resin flow acts on the remaining colored resin, the latterresin is drawn and deformed so that the thickness of the intermediatelayer at the upstream end is changed to assume the shape of a graduallynarrowing thread.

In the invention of claim 17, the pressure and/or velocity of coloredresin supply is gradually increased when the supply is started. In otherwords, volume of the supplied resin or thickness of the intermediatelayer is increased in the upstream direction. In this manner, acolor-gradated portion thus formed shows the shape of a wedge in thedownstream direction at the downstream end.

If the colored resin has a low viscosity in the invention of claim 18,the layer thickness at one end can be changed more effectively to theshape of a gradually narrowing thread. Especially in the case ofelongational deformation, the low viscosity prevents the molten resinfrom being discontinued and more easily makes the change into thegradually narrowing thread.

In the invention of claim 19, the type of valve or the switchingvelocity can be adjusted so that the colored resin pressure is changeddelicately at the confluence when the supply of colored resin begins orcomes to an end. As a result, it is possible for the upstream ordownstream end of the intermediate layer to have the layer thicknesseffectively changed into the shape of a gradually narrowing thread.

In the invention of claim 20, the molding process relates to a practicallaminar structure. The entire preform is made of the same resin, whetherit is colored or not, and stable molding operation can be achieved byusing the same resin.

In the invention of claim 21 the molding process can create the colorgradation effect more visibly by the transmission of light. Thus, thebottle having a new decorative effect can be provided.

The invention according to claims 22 to 27 also relates to apreform-molding process, and in particular, to a preform-molding processwherein the preform is biaxially drawn and blow molded into the bottlehaving a gradation pattern in which colored resin layers are located onboth the inner and outer surfaces of the main resin layer. In theinvention of claim 22, the colored layers made of a colored resin areformed in the shape of double cylinders in the inner- and outer-surfacevicinities by the successive injection molding, with a waiting time setin between. As a result, there can be obtained the preform in whichcolor-gradated portions are formed wherein the thickness of the coloredresin layers is reduced gradually toward the top end of the preform.

If a short waiting time, a fast secondary injection velocity, and a highinjection pressure are used in the invention of claim 23, the layerthickness can be changed slowly to form gradually narrowing threads atthe forefront of colored resin layers.

In the invention of claim 24, the entire preform can be molded by thesame resin. Because the colored resin and the main resin are made of thesame resin, the preform can be molded stably.

In the invention of claim 25, the forefront portion of the colored resinlayers can be changed to the shape of gradually narrowing threads bygiving a low viscosity to the colored resin.

In the invention of claim 26, the molding process can create the colorgradation effect more visibly by the transmission of light. Thus, thebottle having a new decorative effect can be provided.

In the invention of claim 27, a predetermined amount of the main resinis injected before the primary injection. Depending on the purpose ofdecoration for the bottle, it is possible to set arbitrarily theposition of colored resin layers on the preform. In addition, the outer-and inner-surfaces can be covered with the main resin. Since thecontents are not in direct contact with the colored resin, the user mayfeel at ease in using the bottle.

The invention according to claims 28 to 32 also relates to apreform-molding process, and in particular, to a preform-molding processwherein the preform is biaxially drawn and blow molded into the bottlehaving multiple colored resin layers of a laminar structure, in whicheach layer is made of a colored resin of a different color shade, andhaving a gradation pattern in which the thickness of these colored resinlayers is reduced gradually in the upward or downward direction. In theinvention of claim 28, the second resin wedges its way through thecentral part of the earlier injected colored resin, and the flow actionof the second resin allows the layer of the earlier injected coloredresin to form a color-gradated portion having thickness graduallyreduced toward the bottom. Preforms in various laminar structures can beobtained by the variations in the successive molding process. Bottlesnewly decorated in colors and with various patterns can be obtained bybiaxially drawing and blow molding these preforms.

In the invention of claim 29, a combination of injection speed andinjection pressure, among other conditions of successive injections, canbe used to control the extent of gradations caused by the change inthickness of the colored resin layers relatively easily.

The invention of claim 30 is a process for injecting resins successivelyin 3 steps. This process can be accomplished relatively easily from thepoints of view of equipment and process steps. Two or three resins canbe combined in various embodiments including color shades of the coloredresins, depending on the purpose of decorations.

In the invention of claim 31, the colored resin has such a low level ofviscosity that the color-gradated portions are effectively fowled, thusenabling the thickness of the colored resin layers to be changed intothe shape of a gradually narrowing thread in the vertical section of thebody wall.

In the invention of claim 32, the transparent resins make it possible tocreate the gradation effect more visibly by the transmission of light.Thus, the bottle with a new decorative effect can be provided.

The invention of claim 33 relates to a preform, which can be used toprovide the bottle having new decorativeness in which highlysophisticated color gradations caused by the changes in color density,color shade, or both are created by the colored resin layer or layerswhen the preform is biaxially drawn and blow molded into the bottle.

The invention of claims 34 and 35 relates to a bottle having a gradationpattern. In the invention of claim 34, there can be provided a bottlehaving new decorativeness in which highly sophisticated gradationscaused by the changes in color density, color shade, or both can becreated by the colored resin layer or layers.

In the invention of claim 35, it is possible to provide a PET resinbottle having new decorativeness, in which gradations are created inthree colors by the continuous and gradual changes in color density andcolor shade.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall view of the bottle in the first embodiment of thisinvention, with a part of the wall layer shown in an enlarged verticalsection.

FIG. 2 is a front elevational view of the preform in the firstembodiment of this invention, with the irregularly cut right halfportion being shown in a vertical section.

FIG. 3 is a front elevational view of the preform in the secondembodiment of this invention, with the irregularly cut right halfportion being shown in a vertical section.

FIG. 4 is an overall view of the bottle in the second embodiment of thisinvention, which is obtained by biaxially drawing and blow molding thepreform of FIG. 3.

FIG. 5 is a front elevational view of the preform in the thirdembodiment of this invention with the irregularly cut right half portionshown in a vertical section.

FIG. 6 is an overall view of the bottle in the third embodiment of thisinvention, which is obtained by biaxially drawing and blow molding thepreform of FIG. 5.

FIG. 7 is a vertical section showing an example of multiple nozzlesection to be used in the molding process of this invention.

FIG. 8 is a vertical section showing the multiple nozzle section of FIG.7 in the state in which a hot runner block has been fitted to thissection.

FIG. 9 is an explanatory diagram showing the first example of theinjection pattern for molding the preform of this invention.

FIG. 10 is an explanatory diagram showing the steps of filling the moldcavity with molten resins in the injection pattern of FIG. 9.

FIG. 11 is a front elevational view of the preform in the fourthembodiment of this invention, molded according to the injection patternof FIG. 9, with a part being shown in the vertical section.

FIG. 12 is a front elevational view of the bottle in the fourthembodiment of this invention, obtained by biaxially drawing and blowmolding the preform of FIG. 11.

FIG. 13 is an explanatory diagram showing the second example of theinjection pattern for molding the preform of this invention.

FIG. 14 is a front elevational view of the preform in the fifthembodiment, molded according to the injection pattern of FIG. 13, with apart being shown in the vertical section.

FIG. 15 is a front elevational view of the bottle in the fifthembodiment, obtained by biaxially drawing and blow molding the preformof FIG. 14.

FIG. 16 is a schematic explanatory diagram showing the third example ofthe injection pattern for molding the perform of this invention.

FIG. 17 is a vertically-sectional front elevational view showing anexample of the mold for use in the preform molding.

FIG. 18 is a cross-sectional plan view taken along the line A-A in FIG.17.

FIG. 19 is a schematic explanatory diagram showing the process steps offilling the mold cavity with molten resins according to the injectionpattern of FIG. 16.

FIG. 20 is a front elevational view of the preform in the sixthembodiment of this invention, molded by the injection pattern of FIG.16, with a part shown in a vertical section.

FIG. 21 is a front elevational view of the bottle in the sixthembodiment, obtained by biaxially drawing and blow molding the preformof FIG. 20.

FIG. 22 is a schematic diagram showing the fourth example of theinjection pattern for molding the perform of this invention.

FIG. 23 is a schematic diagram showing the fifth example of theinjection pattern for molding the perform of this invention.

FIG. 24 is a series of schematic diagrams showing the steps of fillingthe mold cavity with molten resins according to the injection pattern ofFIG. 23.

FIG. 25 is a front elevational view of the preform in the seventhembodiment of this invention, molded by the injection pattern of FIG.23, and shown partly in vertical section.

FIG. 26( a) is a front elevational view of a bottle in the seventhembodiment of this invention, obtained by biaxially drawing and blowmolding the preform of FIG. 25. FIG. 26( b) is a vertical section ofbottle wall, partly enlarged in the lateral direction.

EXPLANATION OF CODES

-   1. Mold-   2. Core mold-   3. Cavity mold-   4. Cavity-   5. Gate-   11. Multiple nozzle section-   12 a. Feed channel for the main resin-   12 b. Feed channel for the colored resin-   14 a 1, 14 a 2, 14 b. Manifold-   15. Inner flow channel-   16. Middle flow channel-   17. Outer flow channel-   18. Confluence-   19. Joined flow channel-   20. Shut-off pin-   21. Hot runner block-   22 a. Main resin feed port-   22 b. Colored resin feed port-   23 a. Main resin channel-   23 b. Colored resin channel-   25. Check valve-   A. Main resin loader-   B. Colored resin loader-   31. Main resin-   32 (32 f, 32 s, 32 t). Colored resin-   32 a, 32 b, 32 fa, 32 fb. Mold surface vicinity-   32 c, 32 fc. Central part of the cavity-   33. Forefront-   101. Preform-   102. Main resin layer-   103 (103 f, 103 s, 103 t). Colored resin layer-   103 e. Thick end-   103 d. Downstream end-   103 u. Upstream end-   103 m. Intermediate layer-   104. Neck-   105. Neck ring-   106. Body-   107. Bottom-   108. Downstream end-   109. Upstream end-   110 (110 f, 110 s). Color-gradated portion-   110 a. Base-   201. Bottle-   202. Main resin layer-   203 (203 f, 203 s, 203 f). Colored resin layer-   203 e. Thick end-   203 m. Intermediate layer-   204. Neck-   205. Neck ring-   205 a. Shoulder-   206. Body-   207. Bottom-   209. Color-decorated portion-   210. Color-gradated portion-   h1, h2. Height range-   Wf1, Wf2, Ws. Range-   hf, hs. Height range-   Jp. Preliminary injection-   J1. Primary injection-   J2. Secondary injection-   J3. Tertiary injection-   t1 to t4. Time

PREFERRED EMBODIMENTS OF THE INVENTION

This invention is further described with respect to the preferredembodiments of the preform-molding process, the preform, and the bottle,now referring to the drawings. The first embodiment (FIG. 2), the secondembodiment (FIG. 3), and the third embodiment (FIG. 5) of the preform ofthis invention, as well as the first embodiment (FIG. 1), the secondembodiment (FIG. 4), and the third embodiment (FIG. 5) of the bottle ofthis invention, are described, referring to FIGS. 1 to 6.

FIG. 1 is an overall view of the bottle 201 in the first embodiment ofthis invention, with a part of the wall layer shown in an enlargedvertical section, which bottle has been biaxially drawn and blow moldedfrom the preform in the first embodiment of this invention. The bottle201 comprises a body 206 in a bottomed cylindrical shape, shoulder 205 aat the upper end of the body 206, and a neck 204 having screw threadnotched on the outer peripheral wall and having a brim-like neck ring205 at the lower end of the neck 204. The lower half of the body 206 hasa laminar structure in which the main resin layer 202 is laminated withthe colored resin layer 203. The area at the upper end of thecolor-decorated portion 209 created by the colored resin layer 203 inthe lower half of the body 206 is the color-gradated portion 210 createdin the thin boundary area 203 e.

As shown in the embodiment of FIG. 1, the color-gradated portion 210 isdisposed in the central area of the body 206, and the gradateddecoration is quite effectively displayed.

FIG. 2 is a front elevational view of the preform 101 in the firstembodiment of this invention, with about a half shown irregularly in avertical section. This preform 101 comprises a cylindrical body 106closed at its lower end by a semi-spherical bottom 107 having a gateimprint at the bottom center and a cylindrical neck 104 having a screwthread notched on the outer peripheral wall and having a brim-like neckring 105 at the boundary between the neck 104 and the body 106. Thecolored resin layer 103 is formed by a colored resin when a clear andcolorless main resin and a clear and colored resin are injected. Thethin boundary area 103 e is designed to take a position on the body 106at the upper end of the colored resin layer 103.

The lower end of the colored resin layer 103 is slightly reduced inthickness, but since the lower end is disposed at the bottom 107, thisportion does not serve as a color-decorated portion in the overallappearance of the bottle 106. Since the bottom 107 of the preform 101 ishardly drawn and deformed, it is kept from accelerated wall thinningmovement caused by the elongational deformation. Thus, the bottom 107has no effective function as a decorative portion.

FIG. 3 is a front elevational view of the preform 101 in the secondembodiment of this invention, with about a half shown irregularly in avertical section. The second embodiment is similar to the firstembodiment in its basic structure, but the preform 101 is injected inthe order of a main resin, a colored resin, and again the main resin. Bysetting the injection rates of the first main resin and the coloredresin, it is possible to set the positions of both the upper and lowerend portions of the colored resin layer 103, and especially the positionof the thin boundary area 103 e that is the upper end portion of thecolored resin layer 103 on the body 106.

In this second embodiment, the colored resin layers 103 are formed onboth the outer and inner peripheral wall surfaces of the body 106. Thecolored resin layer 103 on the outer surface is not covered by the mainresin layer 102, but is laid in the exposed state. As a result, even ifthe same colored resin is used, the second embodiment gives strongerexpression of color than the first embodiment does.

FIG. 4 is an overall front elevational view of the bottle 201 of thisinvention, made from the preform 101 shown in FIG. 3. Thecolor-decorated portion 209 derived from the colored resin layer 103 ofthe preform 101 is created in the lower half of the molded body 206. Acolor-gradated portion 210 is formed at the upper end of thecolor-decorated portion 209 to show the decorative effect of colorgradation in that area where the color density gradually becomes lightin the upward direction.

FIG. 5 is a front elevational view of the preform 101 in the thirdembodiment of this invention. The colored resin layer 103 extends fromthe upper end face of the neck 104, i.e., the upper end of the preform101, to the central portion of the body 106 where there is the thinboundary area 103 e in the lower end portion of the colored resin layer103.

In the third embodiment of the preform 101, the thin boundary area 103 eis accurately positioned on the body 106 by setting the timing ofinjecting the colored resin.

FIG. 6 is an overall front elevational view of the biaxially drawn,blow-molded bottle 201 in the third embodiment, made from the preform101 shown in FIG. 5. The color-decorated portion 209 derived from thecolored resin layer 103 of the preform 101 is created in the upper halfof the bottle 201 thus molded. The color-gradated portion 210 isdisposed at the lower end of the color-decorated portion 209 at thecenter of the body 206 where the color density becomes light in thedownward direction. Thus, the color-decorated portion 209 created on thebottle 201 takes the position that is upside-down from that of thebottle 201 in the embodiment shown in FIG. 4.

Reference is made to FIGS. 7 to 15 to describe the injection moldingdevice (FIGS. 7 and 8) involved in the preform-molding process of thisinvention, the first example (FIGS. 9 and 10) and the second example(FIG. 13) of the injection molding pattern used with this device, thepreform 101 in the fourth embodiment (FIG. 11) of this invention and thebottle 202 in the fourth embodiment (FIG. 12), the preform 101 in thefifth embodiment (FIG. 14) and the bottle 202 in the fifth embodiment(FIG. 15), all of which are molded by this injection molding pattern.The first and second examples of the injection molding pattern relate toa simultaneous molding process in which the main resin and the coloredresin are injected at the same time.

FIGS. 7 and 8 schematically show an example of the injection moldingdevice to be used in the preform molding process of this invention. FIG.7 is a vertical section showing an example of multiple nozzle section11, which shows mold 1 fitted to the downstream side of this section.FIG. 8 is a vertical section showing the multiple nozzle section 11 ofFIG. 7 in the state in which a hot runner block 21 has been fitted tothe upstream side of this section.

Main resin is fed into the feed port 22 a from the main resin loader Aand is passed through the main resin channel 23 a inside the hot runnerblock 21. Colored resin is fed into the feed port 22 b from the coloredresin loader B and is passed through the colored-resin channel 23 b.These resins are supplied to the multiple nozzle section 11 at apredetermined timing, are joined together in the multiple nozzle section11, and are allowed to fill the cavity 4 of the mold 1.

Each of the above-described resin loaders A and B is provided with anextruder of the screw type or an accumulator having a plunger fitted tothe head of the extruder.

A check valve 25 is disposed in the colored-resin channel 23 b near theconnection to the multiple nozzle section 11, and this check valve has aback-flow prevention function by the action of a ball valve. This checkvalve 25 can also be installed inside the multiple nozzle section 11.

Inside the multiple nozzle section 11 there are three cylindricallayer-forming channels of inner flow channel 15, middle flow channel 16,and outer flow channel 17, which are concentrically disposed from insideto outside. The main resin is passed through the main resin channel 23 aand a main resin feed channel 12 a connected to the main resin channel23 a, and is distributed between the inner flow channel 15 and the outerflow channel 17 through two manifolds 14 a 1 and 14 a 2, respectively.The colored resin is passed through the colored resin channel 23 b and acolored resin feed channel 12 b connected to the colored resin channel23 b, and is sent to the middle flow channel 16 through a manifold 14 b.

At the confluence 18, the colored resin from the middle flow channel 16is flowed between main resin layers from the inner flow channel 15 andthe outer flow channel 17. A multi-layered molten resin fluid is formedconcentrically within the joined flow channel 19, with the colored resinbeing sandwiched as the intermediate layer between the main resin layersover a certain time span. The joined fluid is injected into cavity 4 ofthe mold 1 to fill the cavity.

FIGS. 9-12 show in a series the preform-molding process described inFIGS. 7 and 8, the preform obtained by this process, and the bottleobtained by biaxially drawing and blow molding the preform. FIG. 9 is aschematic diagram showing the first example of the injection pattern tobe used in the preform-molding process of this invention employing themolding device described above, taking time as the horizontal axis andinjection pressure as the vertical axis. FIG. 10 includes schematicdiagrams showing the resin flow movement in the cavity 4 caused by thisinjection pattern. This invention will be described below, using as anexample a PET resin as the main resin and the same PET resin coloredwith a pigment as the colored resin.

This injection pattern is one of the so-called simultaneous injectionmolding patterns. The main resin is injected at a certain pressure for apredetermined time span (from point C to point D). The colored resin isinjected alongside with the main resin at a certain pressure for acertain period of time (from point E to point F) within thispredetermined time span. In this embodiment, the injection of bothresins starts at the same time, and the injection of colored resin comesto an end on the way at point F.

FIGS. 10( a), 10(b), and 10(c) show the flow state at points F, M, andD, respectively. At point F, approximately a third of the cavity 4 hasbeen filled, and the fluid in the laminar structure has been formed bythe intermediate layer 103 m of the colored resin, which is sandwichedbetween inner and outer layers 102 of the main resin. Since the supplyof colored resin starts at point E simultaneously with the supply of themain resin which starts at point C, the downstream end 103 d of theinter mediate layer 103 m of the colored resin is positioned at theforefront of the fluid. (See FIG. 10( a)).

The supply of colored resin is stopped at point F, and from that pointon, only the main resin is supplied. At that time, a part of the coloredresin remaining near the confluence 18 of the middle flow channel 16 ispulled by the flow of the main resin coming from the inner flow channel15 and the outer flow channel 17. As a result, the thickness of theintermediate layer 103 m is reduced slowly so that the intermediatelayer 103 m has the shape of a gradually narrowing thread extending inthe upstream direction at the upstream end 103 u, as shown in FIG. 10(b). When only the main resin is further supplied, the preform thusobtained takes the shape shown in FIG. 10( c) at point D.

In the case of the device shown in FIG. 8, a check valve 25 having aback-flow prevention function by means of a ball valve is disposedbetween the colored resin feed channel 12 b and the colored resinchannel 23 b (See FIG. 8). If the supply of colored resin from the resinloader B is stopped, then the ball of this check valve 25 moves in amoment and works to block the flow channel. As a result, the pressure ofthe colored resin inside the colored resin feed channel 12 b drops in ashort period of time, and the supply of colored resin to the confluence18 comes to an end. The colored resin near the confluence 18 inside themiddle flow channel 16 deforms and extends and moves to the joined flowchannel 19, passing through the confluence 18. The joined resin flowsinto the cavity 4. As shown in FIG. 10( b), the thickness of theintermediate layer 103 m is reduced at the upstream end 103 u in theupward direction to assume the shape of a gradually narrowing thread.

This check valve 25 enables the colored resin to be stopped with highprecision as previously determined for each shot. Thus, the coloredresin can be formed into the intermediate layer 103 m at a predeterminedlocation of the preform at predetermined distribution of layerthickness. From the viewpoint of precision in each shot, the coloredresin should not have a long channel from the check valve 25 to theconfluence 18, but preferably should be as short as possible. If thechannel were long, it would take much time for the pressuretransmission, or the pressure would be deviated greatly because of aviscoelastic effect of the resin.

If a valve used does not work at once but has time lag to shut off thechannel completely, as is the case with spool valve, then gradationcaused by the change in thickness will show a different pattern. Theinjection pattern can be combined with the valve type and the switchingpattern arbitrarily to form various gradation patterns for any purpose.

FIG. 11 is a front elevational view of the preform 101 in the fourthembodiment of this invention that has been molded by the injectionpattern of FIG. 9, using the device of FIGS. 7 and 8, with a part of thepreform shown in a vertical section. The intermediate layer 103 m ofcolored resin spreads over the entire wall, due to a fountain floweffect, at the upper end of the neck 104. The intermediate layer 103 mhas roughly the same thickness in the height range, h1, from the neck104 to the upper portion of the body 106. On the contrary, in the heightrange, h2, beneath h1, down to a level near the bottom 107, the layerthickness decreases to assume the shape of a gradually narrowing thread,thus forming a color-gradated portion 110 caused by the change inthickness of the intermediate layer 103 m.

In this embodiment, the color-gradated portion 110 has the length, L, of54 mm (with the total length of the preform 101 being 100 mm). At thebase level 110 a of the color-gradated portion 110, the intermediatelayer 103 m has the thickness, t1, of 0.9 mm. As an index for the extentof color gradation, the preform has an L/t1 of 60. This embodiment wassuccessful in accomplishing a new type of color gradation caused by thechange in layer thickness to assume the gradually narrowing threadshape.

FIG. 12 shows the bottle 201 having the cylindrical body 206, which hasbeen biaxially drawn and blow molded from the preform 101 of FIG. 11.The bottle is deeply colored in the height range h1 from the top of theneck to the level beneath the neck ring 205. In the height range h2,below h1 where color is dark, the extent of coloration changes slowly tothe colorless, transparent state to form a color-gradated portion 210.The bottom 207 and its neighborhood are a clear colorless area.

In the preform 101 of FIG. 11, the intermediate layer 103 m has analmost uniform thickness in the upper portion of the body 106 in theheight range h1. This portion corresponds exactly to the shoulder 205 aof the bottle 201. Because the lateral draw ratio increases gradually inthe downward direction in the shoulder 205 a, the color-gradated portion210 also includes this shoulder 205 a of the bottle 201.

Like FIGS. 9-12, FIGS. 13-15, too, show in a series the preform-moldingprocess described in FIGS. 7 and 8, the preform obtained by thisprocess, and the bottle obtained by biaxially drawing and blow moldingthe preform.

FIG. 13 is a schematic diagram showing the second example of theinjection pattern to be used in the preform-molding process of thisinvention. This injection pattern is also one of the simultaneousinjection patterns. The main resin is injected at a predeterminedpressure in a specified time span (from point C to point D). The coloredresin is injected alongside with the main resin at a certain pressurefor a certain period of time (from point E to point F) within this timespan (from point C to point D).

FIG. 14 is a front elevational view of the preform 101 in the fifthembodiment of this invention that has been molded by the injectionpattern of FIG. 13, with a part shown in a vertical section. Theintermediate layer 103 m has roughly the same thickness in the heightrange h1, starting from the lower portion of the body 106. In the heightrange h2, above h1, the thickness decreases in the shape of a wedge inthe upward direction, thus forming a color-gradated portion 110 causedby the change in thickness.

This color-gradated portion 110 is presumably formed in the neighborhoodof the confluence at point E where the injection of colored resin beginsas shown in the injection pattern of FIG. 13. At point E, the coloredresin starts being brought in through the middle flow channel 16. Whenthe colored resin flows in between the layers of main resin coming fromthe inner flow channel 15 and the outer flow channel 17, the forefrontis found to assume the shape of a wedge.

FIG. 15 shows the bottle 201 having the cylindrical body 206 in thefifth embodiment of this invention, which has been obtained by biaxiallydrawing and blow molding the preform 101 of FIG. 14. In the height rangeh1, the body wall is colored almost uniformly. In the height range h2,the coloration gradually changes to the colorless and transparent state,and forms the color-gradated portion 210. In the area above the heightrange h2, the wall is colorless and clear.

The extent of color gradation of the bottle 201 in the fifth embodimentdescribed above does not change so gradually as in the fourthembodiment. However, the change in thickness of the intermediate layer103 m in the color-gradated portion 110 of the preform 101 can be mademore gentle as by giving the colored resin a lower level of viscositythan the main resin, by raising the pressure further gradually at pointE of the injection pattern, or by employing a check valve that can beopened gradually.

Reference was made to FIGS. 7-15 to describe the preform-molding processrelated to the simultaneous injection molding, and the embodiments ofthe preform and the bottle. But it is to be understood by those skilledin the art that this invention is not limited to these embodiments. Thesynthetic resin to be used in this invention is not limited to the PETresin, but it is also possible to utilize the PP resin and the like,which have been used in conventional biaxially drawn, blow moldedbottles. The molten viscosity of the colored resin can be changed forany purpose. The resins used in this invention need not necessarily beof the same type, but other types of resins can also be used. Forexample, a resin having a high gas barrier property, such as a nylonresin, can be utilized as the colored resin to provide a bottle havingthe high gas barrier property, in addition to the sophisticateddecorations caused by color gradation.

In the foregoing description of preferred embodiments shown in FIGS.7-15, the color-gradated portion was formed at either upstream ordownstream end. However, depending on the purpose, it is also possibleto form the color-gradated portions at both ends. Even multiplecolor-gradated portions can be formed in the upward and downwarddirections of the bottle, by injecting colored resins intermittentlymore than once within the predetermined time span, in which the mainresin is injected. The above-described embodiments employed a moldingdevice provided with a multiple nozzle section that passes 2 resingroups through 3 layer-forming channels. Another middle flow channel canbe added for use by an additional intermediate layer. Colored resins ofdifferent colors can be supplied to these two middle flow channels toform color-gradated portions having different colors on the upstream anddownstream sides or to superimpose the colors. It should be noted herethat the main resin is not limited to colorless, transparent materials,but can be colored and transparent or opaque, depending on the purpose.

The middle flow channel for the colored resin is not limited to acylindrical shape, but the cross-section may have the shape of a thinrectangle. In this case, the bottle is decorated with the intermediatelayer having vertical strips of color-gradated portion in apredetermined area of the bottle.

Now reference is made to FIGS. 16-22 to describe the third example(FIGS. 16 and 19) and the fourth example (FIG. 22) of the injectionmolding pattern, the preform in the sixth embodiment (FIG. 20) of thisinvention molded by the third example of the injection molding pattern,and the bottle 201 in the six embodiment (FIG. 21) obtained by biaxiallydrawing and blow molding this preform 101. The third and fourth examplesof the injection molding pattern are used in the successive moldingprocess in which the main resin and the colored resin are injectedsuccessively.

FIG. 16 is a schematic explanatory diagram showing the third example ofthe successive injection pattern to be applied to the preform-moldingprocess of this invention. FIGS. 17 and 18 are sectional views of themold used in the preform-molding process of this invention.

The mold 1 shown in FIGS. 17 and 18 comprises a core mold 2 and a cavitymold 3, which are combined with each other to form a cavity 4 in theshape of a test tube. A gate 5 is disposed at the position opposed tothe central part of bottom 107 of the preform 101 (See also FIG. 20).Molten resins are supplied from this gate 5, and are injected into thecentral part of bottom 107 (See also FIG. 16) of the preform 101according to the injection pattern shown in FIG. 16. The injected resinsmove thorough the cavity 4 toward the portion corresponding to the neck104 to fill the cavity 4.

FIG. 16 schematically shows an example of the successive injectionpattern. The primary injection J1 of the colored resin 32 is given for aperiod ranging from t1 to t2. After a lapse of waiting time Ht rangingfrom t2 to t3, the secondary injection J2 of the main resin 31 is givensuccessively for a period ranging from t3 to t5.

FIGS. 19( a), 19(b), and 19(c) are schematic diagrams showing theconditions of resins at time points t2, 14, and 15, respectively, of theabove-described injection pattern. At point t2, about a fourth of thecavity 4 upward from the bottom has been filled with a short shot ofcolored resin 32 (See FIGS. 17, 18, and 19(a)).

Then, the supply of colored resin is brought to a halt at point t2 underthe above-described filling condition. With the progress of the waitingtime Ht (from t2 to t3), the short shot of the injected colored resin 32starts to cool on the surfaces and in the vicinities of the cavity mold3 and the core mold 2 (32 a, 32 b) (See an enlarged view in FIG. 8), andthe cooling/solidification of the resin or an increase in the moltenviscosity goes on in these parts.

The secondary injection J2 of the main resin 31 is successively givenunder this cooled condition. As schematically shown in FIG. 19( b), themain resin 31 in the molten state is passed through the gate 5 locatedat the position opposed to the center of the bottom 107 of the preform101 and through the high-temperature portion of the colored resin 32 inthe central part 32 c of the cavity 4 (See the enlarged view of thecavity in FIG. 18). Then, the main resin 31 breaks through the forefront33 of the colored resin 32, and goes on to move toward the portioncorresponding to the upper part of the neck 104 (See outline arrows inFIG. 19( b)), while deforming and dragging a part of the colored resin32 together. The main resin 31 further flows in and goes into the stateshown in FIG. 19( c) at point t5.

At that time, the colored resin 32 located quite near the mold surfaceshardly flows, but remains at the position of primary injection 31. Onthe other hand, the colored resin 32 located at the center 32 c deformsand flows as it is dragged in the flow direction. In this example, themain resin 31 breaks through the forefront 33 of the colored resin 32,as shown in FIG. 19( b), but the forefront 33 need not be necessarilybroken through. Depending on the purpose of decoration, the main resin31 can be flowed without breaking through the forefront 33.

FIG. 20 is a front elevational view, with partly a vertical section, ofthe preform 101 in the sixth embodiment, molded by the above-describedsuccessive injection molding process, using the main resin 31 made of aPET resin and the colored resin 32 made of the same PET resin exceptthat it is colored. This preform 101 has colored layers 103 in the shapeof double cylinders in the inner- and outer-surface vicinities. Thecolored layers have an almost constant thickness in the height range h1corresponding roughly to the lower half of the preform 101. In theheight range h2, the thickness changes to assume the shape of agradually narrowing thread, thus creating color-gradated portions 110caused by reducing the thickness gradually in the upward direction.

FIG. 21 shows a bottle 201 having cylindrical body 206 in the sixthembodiment of this invention, which is obtained by biaxially drawing andblow molding the preform 101 of FIG. 20. The bottle is deeply colored inalmost the same color density in the height range h1 from the bottom 207to roughly half the body height. In the height range h2, above h1, up tothe level directly beneath the neck ring 205, there appears acolor-gradated portion 210 caused by the change in color density, wherethe extent of coloration changes slowly to the colorless, transparentstate. The uppermost area including the neck 204 is a clear colorlessarea.

This invention has been described with respect to the preform-moldingprocess involving the successive injection molding, and the preferredembodiments of the preform and the bottle while referring to FIGS.16-22. but it is to be understood by those skilled in the art that thisinvention is not limited to these embodiments. The synthetic resin to beused in this invention is not limited to the PET resin, but it is alsopossible to utilize the PP resin and the like, which have been used inconventional biaxially drawn, blow molded bottles. The molten viscosityof the colored resin can be changed for any purpose. The colored resinused in this invention need not necessarily be of the same type, butother types of resins can also be used. The main resin need not becolorless and transparent, but can be colored, and transparent,translucent, or opaque.

In addition to the injection pattern described in FIG. 16 and used inthe successive injection molding, other injection patterns can beutilized for any purpose. FIG. 22 shows the fourth example of theinjection pattern that can be applied to this invention. In thispattern, a preliminary injection Jp of the main resin 31 is given in apredetermined amount before the primary injection J1. This preliminaryinjection Jp of the main resin makes it possible to raise the lower endposition of each colored resin layer 103 in response to the injectedamount of the main resin and to change the position of colored resinlayers 103, depending on the purpose of decoration for the bottle 201,without limiting the lower end to the level shown in the embodiment ofFIG. 20 where the lower end is set at the bottom 107.

Furthermore, at the time of primary injection J1 of colored resin afterthe preliminary injection Jp, the colored resin is forced to passthrough the central part of a short shot of the main resin that has beeninjected preliminarily, while dragging this main resin over the moldsurfaces. In this manner, both the outer surface (outermost layer) andthe inner surface (innermost layer) can be configured with this mainresin, depending on the condition of injection. Since the contents ofthe bottle do not come in direct contact with the colored resin, theuser feels at ease in utilizing the bottle.

Reference is made to FIGS. 23-25 to describe the fifth example of theinjection molding pattern (FIGS. 23), the preform 101 in the seventhembodiment (FIG. 25) of this invention, which is molded according to thefifth example of the injection pattern, and the bottle 201 in theseventh embodiment (FIG. 26) obtained by biaxially drawing and blowmolding this preform 101. The fifth example of the injection moldingpattern is based on the successive molding process in which multipleresins are successively injected.

FIG. 23 is a schematic diagram explaining the fifth example of thesuccessive injection pattern which is applied to the preform-moldingprocess of this invention. The preform is molded by using the mold shownin FIGS. 17 and 18.

The mold 1 shown in FIGS. 17 and 18 comprises a core mold 2 and a cavitymold 3. A cavity 4 corresponding to the preform in the shape of a testtube is formed inside the mold 1. Gate 5 is located at the positionopposed to the central part of bottom 107 (See also FIG. 25.) of thepreform 101. Molten resins are supplied through this gate 5 and areinjected according to the injection pattern shown in FIG. 23. The firstinjected resin flows through the cavity 4 toward the portioncorresponding to the neck 104 to fill the cavity 4.

The injection pattern schematically shown in FIG. 23 is an example ofthe successive injection pattern, in which colored resins 32 f, 32 c,and 32 t are successively injected into the cavity in 3 steps of primaryJ1 (from time t1 to time t2), secondary J2 (from time t2 to time t3),and tertiary J3 (from time t3 to time t4).

FIGS. 24( a), 24(b), and 24(c) are schematic diagrams explaining theinjection pattern at the time points of t2, t3, and t4, respectively. Atpoint t2, a third of the cavity 4 has been filled with the colored resin32 f that was injected through the gate 5 in the state of a short shot(See FIGS. 24( a)).

The primary injection J1 is brought to a halt at point t2 under theabove-described filling condition, and the supply of the colored resin32 f is shut off. Then, the secondary injection J2 is subsequentlystarted, and the colored resin 32 s flows into the cavity 4 through thegate 5. The second resin 32 s wedges its way through the central part ofthe first resin 32 f, and moves through the cavity 4 toward the portioncorresponding to the neck 104. At point t3 when the secondary injectionJ2 is brought to a halt, the two resins are in such a state as shown inFIG. 24( b).

As a result of the flow of the colored resin 32 s that has been injectedat the time of the secondary injection J2, the colored resin 321 fromthe primary injection J1 assumes the shape of double cylinders togetherwith the colored resin 32 s over the range of Wf1 shown in FIG. 24( b).In this range, the thickness of the colored resin 321 decreasesgradually in the upstream direction (toward the position of the gate 5).

A tertiary injection J3 is then started subsequently, and a coloredresin 32 t flows into the cavity 4 through the gate 5. This time, thecolored resin 32 t wedges its way through the central part of thecolored resin 32 s and moves through the cavity 4 toward the portioncorresponding to the neck 104. At point t4 when the tertiary injection13 is brought to a halt, the three resins are in such a state as shownin FIG. 24( c)

As a result of the flow of the colored resin 32 t that has been injectedat the time of the tertiary injection J3, the colored resin 32 s fromthe secondary injection J2 assumes the shape of double cylinderstogether with the colored resin 32 t over the range of Ws shown in FIG.24( c). In this range, the layer thickness of the colored resin 32 sdecreases gradually in the upstream direction. At the same time, theportion of the colored resin 32 f in the double cylinders furtherextends over the range of Wf2.

FIG. 25 is a front elevational view, partly a vertical section, of thepreform in the seventh embodiment of this invention, in which the samePET resin has been used in the primary injection J1, the secondaryinjection J2, and the tertiary injection J3, but in different colors:yellow, pale blue, and light red for the colored transparent resins 321,32 s, and 32 t, respectively. The preform 101 was molded by thesuccessive molding process described above.

The preform comprises, from top to bottom, a yellow layer 103 f, a paleblue layer 103 s, and a light red layer 103 t. In the height range hf,the colored resin layer 103 f assumes the shape of double cylinders, andforms a color-gradated portion 110 f caused by the change in layerthickness, which is gradually reduced toward the bottom 107. In theheight range hs, the colored resin layer 103 s also assumes the shape ofdouble cylinders, and forms a color-gradated portion 110 s caused by thechange in layer thickness, which is gradually reduced toward the bottom107.

FIG. 26( a) shows a bottle 2 having a cylindrical body 206 in theseventh embodiment of this invention, which was obtained by biaxiallydrawing and blow molding the preform 101 of FIG. 25. FIG. 26( b) is avertical section of the body wall which has been partially enlarged inthe lateral direction to explain the laminar structure of the coloredresin layers 203. In the bottle 201, the laminated layers 203 f, 203 s,and 203 t, which are colored respectively in yellow, pale blue, andlight red, are the counterparts of the three colored resin layers 103 f,103 s, and 103 t of the preform 101 shown in FIG. 25, and are formed bybiaxially drawing and blow molding the preform 101 of FIG. 25.

As a whole, the bottle 201 is transparent, but color gradations causedby the changes in color density and color shade have been created in thewall of the bottle 201. In more details, the area from the neck 204 tothe shoulder 205 a is yellow-colored and transparent. Gradationsassociated with color density appear in the shoulder 205 a, with colordensity beginning to dilute downward because of the drawing that changesthe wall thickness in the shoulder 205 a. In the height range h1, theyellow-colored layer 203 f and pale blue colored layer 203 s overlap,and the color changes in this body portion gradually from green to paleblue in the downward direction.

The height range h2 beneath the height range h1 corresponds to the areawhere the height range hs of the preform 101 was drawn. In this rangeh2, the pale blue colored layer 203 s and the light red colored layer203 t overlap, and a purple color becomes more of a red color graduallyin the downward direction. Although the yellow colored layer 103 f alsoextends to the height range h2, the layer thickness is already quitethin, and there is little effect of 103 f on the color shade. If thecolored resins 32 s and 32 t were given a higher color density, then inthe height range h1, for example, there would be a larger effect of thecolored resin 32 s, and the gradation caused by the shades of yellow andblue would not be created vibrantly. Therefore, in this embodiment, thecolored resins 32 s and 32 t had a pale blue color and a light redcolor, respectively.

This invention has been described with respect to the preform-moldingprocess of this invention involving the successive injection molding,and the preferred embodiments of the preform and the bottle whilereferring to FIGS. 23-26, but it is to be understood by those skilled inthe art that this invention is not limited to these embodiments. Thesynthetic resins to be used are not limited to the PET resin, but thoseresins that are conventionally used in the biaxially drawn, blow moldedbottles, such as the PP resins, can also be utilized. The moltenviscosity of colored resins can be changed, depending on the purpose ofuse. The resins need not be of the same type, and the resins of othertypes can be used.

In the above-described embodiment, resins were injected successively inthree steps. However, resins can also be injected in two or four steps,depending on the purpose. In the successive 3-step injections, variousresins can be combined in addition to a combination of a coloredtransparent resin, a transparent resin of a different color, and atransparent resin of still another color. For example, combinationsdescribed below can be utilized.

(1) A colorless transparent resin/A colored transparent resin/Acolorless transparent resin(2) A colored transparent resin/A colorless transparent resin/Atransparent resin of the same color(3) A colored transparent resin/A colorless transparent resin/Atransparent resin of a different color(4) A colored transparent resin/A transparent resin of a differentcolor/A colorless transparent resin

INDUSTRIAL APPLICABILITY

The preform-molding process of this invention can be used to provide abottle having new decorativeness in which highly sophisticatedgradations caused by the changes in color density, color shade, or bothare created by the colored resin layer or layers. This process enablesthe bottle products to be differentiated from other bottle products, andtherefore, wide use applications are expected.

1. A process for injection molding a preform in a shape of a test tube,comprising: flowing molten synthetic resins through at least threelayer-forming channels comprising a cylindrical inner flow channel, amiddle flow channel, and a cylindrical outer flow channel; flowing themolten synthetic resins through a confluence disposed downstream of theat least three layer-forming channels and through a joined flow channel;passing the molten synthetic resins through a gate disposed at aposition opposed to a center of a bottom of a preform to be molded; andinjecting the molten synthetic resins into a mold to form the preform;supplying each of the inner flow channel and the outer flow channel witha supply of a main resin for the preform from at least one first loaderat a predetermined time span, pressure, or velocity; supplying themiddle flow channel with a supply of a colored resin from a secondloader at a predetermined pressure and/or velocity during apredetermined time within the predetermined time span; allowing thecolored resin to join the main resin from the inner flow channel and themain resin from the outer flow channel at the confluence in such amanner that a layer of the colored resin is sandwiched between twolayers of the main resin; forming a multi-layered molten resin fluidhaving an intermediate layer of the colored resin between the two layersof the main resin within the joined flow channel over a certain span oftime; adjusting an injection pattern including at least one of a time ofstarting and ending the supply of the colored resin, pressure andvelocity profiles; and gradually reducing a thickness of theintermediate layer at an upstream or a downstream point of flow in anupstream or a downstream direction so as to form a color-gradatedportion caused by a change in the thickness.
 2. The process forinjection molding a preform according to claim 1, wherein the middleflow channel is disposed coaxially as a cylindrical channel togetherwith the inner flow channel and the outer flow channel.
 3. The processfor injection molding a preform according to claim 1, wherein supplypressure and/or velocity is gradually reduced when the supply of thecolored resin comes to an end, so that a color-gradated portion isformed at an upstream end of the intermediate layer.
 4. The process forinjection molding a preform according to claim 1, wherein the coloredresin remains in a vicinity of the confluence where the colored resinjoins the main resin when the supply of the colored resin comes to anend and, wherein the colored resin that remains is dragged by a flow ofthe main resin in the downstream direction to form a color-gradatedportion at an upstream end of the intermediate layer.
 5. The process forinjection molding a preform according to claim 1, wherein supplypressure and/or velocity is gradually increased when the supply of thecolored resin is started, so that a color-gradated portion is formed ata downstream end of the intermediate layer.
 6. The process for injectionmolding a preform according to claim 1, wherein the colored resin has amolten viscosity that is lower than a viscosity of the main resin sothat the intermediate layer of the multi-layered molten resin fluid isdeformed to assume a shape of a gradually narrowing thread at either anupstream end or a downstream end of the intermediate layer.
 7. Theprocess for injection molding a preform according to claim 1, wherein avalve to open or close the middle flow channel is disposed between thesecond loader and the middle flow channel and wherein the color-gradatedportion is formed at either a downstream end or an upstream end of theintermediate layer of the multi-layered molten resin fluid, depending ona type of the valve or a switching method.
 8. The process for injectionmolding a preform according to claim 1, wherein there are two loadersconsisting of a first loader and the second loader, and threelayer-forming channels consisting of the inner flow channel, the middleflow channel, and the outer flow channel, wherein the main resin fromthe first loader is supplied to both the inner flow channel and theouter flow channel, and wherein the colored resin from the second loaderis supplied to the middle flow channel.
 9. The process for injectionmolding a preform according to claim 1, wherein both the main resin andthe colored resin are transparent materials.
 10. A process for molding apreform, comprising: injecting a short shot of a primary injection ofcolored resin into a cavity of a mold by way of a gate located at aposition opposed to a center of a bottom of a preform to be molded;after a waiting time from an end point of the primary injection,injecting a secondary injection of main resin; adjusting the waitingtime so that the main resin from the secondary injection is allowed toflow through the cavity in a manner in which the main resin penetrates acentral part of the colored resin located inside the cavity of the mold;forming colored resin layers made of the colored resin in a shape ofdouble cylinders at positions near an inner surface and an outer surfaceof the preform; and forming color-gradated portions where a thickness ofcolored resin layers are reduced in an upward direction of the preform.11. The process for molding a preform according to claim 10, wherein anextent of color gradation caused by the thickness of the colored resinlayers is controlled by a combination of the waiting time, a speed ofsecondary injection, and an injection pressure.
 12. The process forinjection molding a preform according to claim 10, wherein colored mainresin is used as the colored resin.
 13. The process for injectionmolding a preform according to claim 10, wherein the colored resin has alower molten viscosity than a molten viscosity of the main resin. 14.The process for injection molding a preform according to claim 10,wherein both the main resin and the colored resin are transparent resinmaterials.
 15. The process for injection molding a preform according toclaim 10, wherein a preliminary injection of the main resin is injectedin a predetermined amount before the primary injection.
 16. In asuccessive injection process in which multiple resins including at leastone colored resin are successively injected into a cavity of a mold byway of a gate located at a position opposed to a center of a bottom of apreform to be molded, a process for injection molding a preformcomprises: initially injecting a short shot of a colored resin into thecavity of the mold; after the initial injecting, injecting a secondresin and letting the second resin wedge its way through a central partof the initially injected colored resin to form laminated layers; andforming a color-gradated portion wherein a thickness of a colored resinlayer made of the colored resin is gradually reduced toward the bottom.17. The process for injection molding a preform according to claim 16,wherein an extent of gradation associated with the thickness of thecolored resin layer is controlled by a combination of injection speedand pressure of the second resin.
 18. The process for injection moldinga preform according to claim 16, wherein there are three resinsincluding the colored resin and the second resin that are successivelyinjected in 3 steps.
 19. The process for injection molding a preformaccording to claim 16, wherein the colored resin has a lower moltenviscosity than a molten viscosity of the second resin.
 20. The processfor injection molding a preform in according to claim 16, wherein eachof the colored resin and the second resin is transparent.